<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>增强表单-属性</title>
</head>
<body>
    <!-- autofocus:自动获取焦点  required:必填  multiple:可以填写多个-->
    <form action="">
        用户名:<input type="text" name="userName" autofocus pattern="[0-9][a-z]{3}" placeholder="请输入一个数字,三个小写字母">
        <br>
        邮&emsp;箱:<input type="email" name="email" required multiple>
        <br>
        <input type="submit" value="提交">
    </form>
</body>
</html>